mfd: ab8500-sysctrl: Always enable pm_power_off handler

AB8500 sysctrl driver implements a pm_power_off handler, but that is
currently not registered until a specific platform data field is
enabled.

This patch drops the platform data field and always registers
ab8500_power_off if no other pm_power_off handler was defined before,
and also introduces the necessary cleanup code in the driver's remove
function.

Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Fabio Baltieri <fabio.baltieri@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/ab8500-sysctrl.c

@@ -193,7 +193,7 @@ static int ab8500_sysctrl_probe(struct platform_device *pdev)
 
 	sysctrl_dev = &pdev->dev;
 
-	if (plat->pm_power_off)
+	if (!pm_power_off)
 		pm_power_off = ab8500_power_off;
 
 	pdata = plat->sysctrl;
@@ -228,6 +228,10 @@ static int ab8500_sysctrl_probe(struct platform_device *pdev)
 static int ab8500_sysctrl_remove(struct platform_device *pdev)
 {
 	sysctrl_dev = NULL;
+
+	if (pm_power_off == ab8500_power_off)
+		pm_power_off = NULL;
+
 	return 0;
 }